Field of the Invention
Embodiments of the present invention relate generally to controlling the operating temperature of processors and, more specifically, to techniques for reducing fan cycling.
Description of the Related Art
In computer systems, in general, and with graphics processing units (GPUs) in particular, thermal management has become increasingly critical as processor technology has evolved. In particular, shrinking geometries of modern silicon processes afford higher density of switching transistors. Further, the increasing speed of operation in modern systems leads to increasing switching frequency of transistors. The power dissipated in a silicon device is proportional to the number of switching transistors and also to the switching frequency. Thus, as processor designs have advanced, power dissipation has increased, and attention to thermal management issues has become more paramount.
Computer systems typically include one or more mechanical fans to provide convection cooling of dissipating components. However, a fan that operates continuously can create an annoying environment for the user. To reduce this annoyance, some thermal management systems cause the fan to turn off when the temperature of the system is at a low enough level that cooling is not required. In such a thermal management system, the temperature at which the fan turns off (the “fan-off” temperature) should be lower than the temperature at which the fan turns on (the “fan-on” temperature) to avoid frequent cycling between “on” and “off” states.
One drawback of the above approach is the difficulty in determining an appropriate temperature range between the fan-on temperature and the fan-off temperature. If the difference between the fan-on temperature and the fan-off temperature is too small, then fan cycling can be more frequent, which, as alluded to above, can be annoying to the user. On the other hand, if the difference between the fan-on temperature and the fan-off temperature is too large, then the magnitude of the thermal cycling experienced by the electronic components in the system can increase, which can increase the thermal stresses on those components. Further, if the difference between the fan-on temperature and the fan-off temperature is too large, then the fan may not turn off when it otherwise could.
As the foregoing illustrates, what is needed in the art is a more effective technique for controlling fan operation when cooling a processor.